How to add glossy texture to Principled Shader?
I'm am so new here I hesitate to even chime in, but I have been (and this may not be the right way) adding the mix shader to the output of the principled shader and connecting emission shades to the other mix input with success.  I think it shoukd work with a glossy shader as well, but again I am super new here and this is my Virgin answer so I hope it helps.